1. Field
The present invention relates to an ink cartridge and a method of replenishing an ink cartridge with pigment ink.
2. Background Art
It is known to replenish spent ink cartridges with ink.
However, considering problems ascribable to mixing old and new ink, it is necessary to wash the used ink cartridge before replenishing the ink cartridge with ink.
In addition, when the ink cartridge is replenished without washing the ink cartridge, a way must be found to stabilize mixing of the residual ink and the newly added ink.
Since dye ink has been mainly used in ink cartridges, the re-use of such cartridges has been approached mostly in terms of solving problems with regard to replenishment of the ink cartridge with dye ink or pigment ink into or residual ink in an ink absorbent substance provided in the ink cartridge to obtain a negative pressure.
JP-2008-179804-A discloses filling (replenishing) ink having good preservation stability and discharging stability secured by satisfying the following relationship: B/A≦2, where A represents the number of coarse particles immediately after mixing the newly added ink and residual ink and B, designates the number of coarse particles left for 24 hours.
However, in JP-2008-179804-A, both pigments and dyes are usable as the coloring agent, and neither the pH of the ink nor solution of agglomerated residual pigment ink peculiar to pigment ink were discussed at all.
JP-2002-121435-A discloses a replenishment ink and replenishment method that do not adversely affect the print quality, the ink dischargeability, and the print head, in which the relation of the surface tension, pH, and viscosity of initial newly added ink and newly added ink are regulated.
However, in JP-2002-121435-A mentioned above, although pH was included in the three regulated properties, only dye ink was subjected and the newly added ink had a pH lower than that of the initial newly added ink in some cases.
Consequently, JP-2002-121435-A mentioned above is not suitable either to obtain stable mixing with the newly added ink or to dissolve agglomerated residual ink for an ink cartridge using pigment ink.